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Proceedings Paper

Comparison of MTFs in x-ray CT images between measured by current method and considered linearity in low contrast
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Paper Abstract

Generally, the modulation transfer function (MTF) of a computed tomography (CT) scanner is calculated based on the CT value. However, it is impossible to measure the MTF directly because the CT value is defined as a nonlinear function of the X-ray intensity. Due to this characteristic, the MTF varies with the subject's contrast. Therefore, we measured the MTFs of a CT scanner using high- and low-contrast wire phantoms. We selected thick copper wire in water as the high-contrast subject and thin copper wire in water as the low-contrast subject. The MTF measured with the low-contrast subject was decreased relative to that measured with the high-contrast subject because the CT value was nonlinear. Thus, to evaluate the spatial resolution in a low-contrast subject such as the human body, we should measure the MTF with a low-contrast wire phantom. In addition, by using low-contrast subjects, we can approximately determine the CT value using a linear function.

Paper Details

Date Published: 18 March 2008
PDF: 8 pages
Proc. SPIE 6913, Medical Imaging 2008: Physics of Medical Imaging, 69133O (18 March 2008); doi: 10.1117/12.770112
Show Author Affiliations
Naotoshi Fujita, Nagoya Univ. (Japan)
Katsuhiro Ichikawa, Kanazawa Univ. (Japan)
Takanori Hara, Nakatsugawa Municipal General Hospital (Japan)
Yoshie Kodera, Nagoya Univ. (Japan)


Published in SPIE Proceedings Vol. 6913:
Medical Imaging 2008: Physics of Medical Imaging
Jiang Hsieh; Ehsan Samei, Editor(s)

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